Tar Spot is worse when you have multiple stresses. This can be other diseases, drought stress, lack of nitrogen etc. Therefore, we need to be addressing plant health as a whole, in order to conquer Tar Spot. It is probable that the heavy stalk rot pressure throughout the mid-west is the hidden reason why Tar Spot is rampant.

Applying fungicide a bit late (brown silk) seems to be very effective with Tar Spot. Fungicide will not kill Tar Spot, but will buy you time until the plant dies.

Genetics vary greatly in resistance/susceptibility to Tar Spot. This is critical when you are in a Tar Spot hot spot. There are hybrids that almost resist 100%, and there are hybrids that are very susceptible. Ask your seed rep for guidance in choosing Tar Spot tolerant hybrids.

Higher levels of zinc and copper will tend to help with Tar Spot but be very, very careful and do not over-apply copper. As in most disease pressure, crop rotation, cover crops and residue composition will help with Tar Spot control.

In conclusion we need to be addressing this issue in 3 points:
1. Building Soil Health (Crop rotation, micro-nutrients, cover crops etc.)
2. Genetics (Selecting hybrids that resist Tar Spot and disease in general)
3. Fungicide (A short term Band-Aid to keep from losing crops/profit margins while we work on long term goals.)

This information has been compiled by Prairie Hybrid Seeds and is a combination of multiple people’s experience and observations in the agriculture industry, but does not guarantee results.